presents the predicted limiting-magnitude performance of WFC3 and compares it with that of the ACS camera. The calculations are based on optimal extraction of a point source. The limiting ABMAG at a S/N of 10 was calculated for a 1-hour and a 10-hour exposure. The WFC3 filters used are listed in column 2; for ACS, the most comparable wide-band filter was used and its name is given in column 3. The ACS/HRC camera was assumed for the NUV and U
-band comparison, and ACS/WFC was assumed for B
, and I
gives further details on estimation of exposure times. More accurate estimates require use of the WFC3 Exposure Time Calculator (ETC)
, available online.